The level of activity of each of 4 hydrolases in the brush border of human intestinal mucosa will be determined in per oral intestinal biopsies from patients with various diseases of undetermined etiology. The enzymes will be measured in the crude pellet obtained from the biopsies by use of discriminating substrates previously determined in this laboratory. Studies will begin on the isolation and characterization of the peptide hydrolyzing enzymes in the cytosol of human intestinal epithelial cells. Separation will be attempted by several means including ion exchange chromatography, acrylamide gel electrophoresis, and gel filtration. Peptide hydrolase IIB isolated from the brush border of rat intestinal mucosa will be purified in sufficient quantity to permit direct analysis of metal ion content in hopes of determining the metal ion cofactor for the enzyme.